1. Field of the Invention
The present invention relates to an evaporative cooler and more particularly to an evaporative cooler having an improved irrigation system. It also relates to a method of supplying liquid to an evaporative cooler.
2. Description of the Related Art
Evaporative coolers are known in which a supply of liquid is provided to a porous panel. An air stream passing through the panel can evaporate this liquid. In doing so, the temperature of the air decreases and its humidity is increased. In such prior art devices, the liquid, generally water, was supplied in quantities sufficient to maintain the wettable surface completely saturated. Excess water was allowed to drip away or would be recycled for reuse. Such a device is known from U.S. Pat. No. 6,332,332, which discloses a water distribution tray with an inlet and a series of water outlets. Evaporative coolers of this type have been found to be very inefficient in significantly lowering the temperature of the air stream.
Other evaporative coolers are known in which a primary flow of air on a first side of a heat exchanger is cooled by evaporation of a liquid into a secondary flow of air on a second side of the heat exchanger. An important consideration in such coolers is the supply of liquid for evaporation. One such device is disclosed in PCT publication WO 99/41552, which includes spray means for spraying finely divided fluid onto the walls of a secondary canalization.
It has been found however that nebulization, or spraying finely divided fluid, into the flow channels has a number of disadvantages. From a functional perspective, the presence of liquid droplets in the air stream reduces the capacity of the air stream to evaporate further liquid from the heat exchanger itself. This reduces the cooling effect on the primary flow and considerably reduces the efficiency of the system. Of perhaps greater importance, the
According to an alternative embodiment disclosed in PCT publication WO 99/41552, a pipe system may be used for supplying fluid directly to an absorbent or hygroscopic coating on the heat exchanger. It has however been found that hygroscopic coatings tend to exert excessive retention on the liquid and reduce its ability to evaporate. Additionally, a pipe system capable of evenly distributing liquid over the whole area of the heat exchanger is complicated and the liquid flow from the individual pipe outlets is difficult to control.